Structural and functional features of the taste system change dramatically during development. While much has been learned by studying normal developmental processes, complementary experiments that use experimental manipulations during critical phases of development have been of great value in learning how the taste system is organized. The specific aims of this proposal use coordinated morphological, immunohistochemical, ultrastructural, neurophysiological, and behavioral studies to extend our earlier findings on the development of the gustatory system. Morphological studies examine the development, plasticity, and interrelationships of the terminal fields from three gustatory nerves in the first synaptic relay in the brain, in the nucleus of the solitary tract (NST). Ultrastructural studies will examine the synaptic organization of gustatory nerve terminals with the inhibitory circuitry within the NST. Neurophysiological studies will be used to fully explore the functional development, plasticity, and interrelationships of converging gustatory inputs onto single NST neurons. Behavioral studies will begin to examine how the "reorganized" brain resulting from near life-long dietary sodium restriction is expressed in taste-related behaviors. The overall focus of this proposal, therefore, is on how the central gustatory system is assembled after the initial functional and structural components are present and how taste preferences and aversions are affected by experimentally altered development. Proposed studies will provide new information about: 1) how information from three gustatory nerves make their inputs into the brainstem during normal development and following a dietary manipulation that has widespread effects on the development of peripheral gustatory function and structure, 2) the manner in which the synaptic organization responsible for inhibitory influences is structured in the developing brain, 3) the functional properties of central gustatory neurons as they receive inputs from three separate gustatory nerves, and 4) the behavioral consequences of a "reorganized" brain. Findings from these studies will provide further information about the development and plasticity of the peripheral and central gustatory system, and about the development of taste preferences and aversions. They will also be useful in determining the role that diet has on organizing the developing sense of taste.